Impurities, in particular dissolved halogenated hydrocarbons, must be avoided in boiler feed water, as they cause corrosion in the steam boiler. The DOC (dissolved organic carbon) process is known for the detection of dissolved organic impurities. A disadvantage of this process is that volatile organics and heteroatoms, e.g. acid formers, such as chlorine and sulfur compounds, are not detected.
A process is further known in which the thermal conversion taking place in the boiler is to be imitated in a UV reactor. In this method the conductivity of the water is measured after irradiation. A disadvantage of this process is that, as a result of the UV oxidation, the conversion of e.g. halogenated hydrocarbons to soluble, dissociable components does not take place to the desired extent.